The invention relates to a process and machinery (Preheaters and Recycling Machine) for accurately heating, milling/profiling, handling and placement to grade of 100% Hot In-place Recycled (HIR) asphalt mixed with various types of rejuvenating fluids, liquid polymers and aggregates, with or without the addition of new, virgin asphalt (produced by a standard asphalt plant). The asphalt pavement is heated and softened by two or more Preheaters, physically scarified by one or more sets of carbide cutters (rakes), profiled and collected by mills, measured and mixed with rejuvenating fluid, polymer liquid (if required) and washed aggregate (if required) in a pug mill. The type, and amount of additives required to 100% HIR asphalt pavement is specified by pre-engineering using core samples taken from the asphalt pavement at regular intervals.
The 100% HIR of asphalt pavement is achieved by the addition of rejuvenator fluid, liquid polymers (if required) and washed aggregate (if required). Rejuvenator fluid must be accurately metered, as too much rejuvenator fluid will cause the recycled asphalt to bleed (rejuvenator fluid rising to the surface) softening the compacted surface. Too little fluid will not restore flexibility back into the recycled asphalt.
Liquid polymers such as Latex are added to increase the performance of the 100% recycled asphalt (Superpave specifications) by increasing flexibility while reducing rutting and cracking over a wider operating temperature range.
Adding aggregate (typically washed sand) during the 100% HIR process will modify the asphalt""s physical properties and the air void ratio (percentage of air entrenched in the asphalt and generally specified at between 3-5%).
Adding rejuvenating fluid alone to the recycled asphalt will generally reduce the air-void ratio while adding washed sand tends to increase the air-void ratio. Adding aggregates that contain dust (unwashed) will generally reduce the air void ratio. Pre-engineering determines the correct specification and application rates for rejuvenating fluid, polymer liquid and aggregate. The Recycling Machine is designed with modular pin-on attachments for increased flexibility.
The present invention has a wide range of processing capabilities. For example, it can be used in, among others, the following applications:
1. 100% HIR: The old asphalt pavement is heated by a plurality of Preheaters to soften the asphalt for processing by the Recycling Machine. The final Preheater may be fitted with carbide cutters, asphalt collection blades (rake assembly) and an aggregate distribution system. The old asphalt is physically scarified by carbide cutters (rakes), profiled and collected by mills, measured and mixed with rejuvenating fluid, polymer liquid (if required) and washed aggregate (if required) in a pug mill. In one embodiment of the present invention, as described below, the asphalt from the heated surface does not need to be lifted. The type and amount of additives required to 100% HIR asphalt pavement is specified by pre-engineering using core samples taken from the asphalt pavement at regular intervals.
The 100% HIR of asphalt pavement is achieved by the addition of rejuvenator fluid, liquid polymers (if required) and washed aggregate (if required). Liquid polymers such as Latex are added to increase the performance of the 100% recycled asphalt (Superpave specifications) by increasing flexibility while reducing rutting and cracking over a wider operating temperature range.
Adding aggregate (typically washed sand) during the 100% HIR process will modify the asphalt""s physical properties and the air void ratio (percentage of air entrenched in the asphalt and is generally specified at between 3-5%). The 100% recycled asphalt is placed to grade as a single course (layer) by a standard paving screed (attached to the Recycling Machine).
The Recycling Machine can be equipped with an optional front asphalt hopper/variable speed chain slat conveyor, truck pusher bar, variable speed central belt conveyor and electronic belt scale and conveyor hopper/diverter valve. A surge bin/vertical elevator, auger/divider/strike off blade, and screed assembly are also provided. The Recycling Machine""s mills, pug mill, auger/divider/strike off blade and screed assembly, process and place the 100%, recycled asphalt. When equipped with the optional equipment, the Recycling Machine""s on-board computer meters the new asphalt, which may be stored in a hopper, into the surge bin/vertical elevator, auger/divider/strike off blade and screed assembly for startup. The optional equipment also allows the Recycling Machine to perform the 100% HIR Remix method.
2. 100% HIR (Remix): In this application, the old asphalt pavement is heated by three or more Preheaters to soften the asphalt for processing by the Recycling Machine. The final Preheater may be fitted with carbide cutters, asphalt collection blades (rake assembly) and an aggregate distribution system. The Recycling Machine can be equipped with a front asphalt hopper/variable speed chain slat conveyor, truck pusher bar, variable speed central belt conveyor and electronic belt scale, conveyor hopper/diverter valve, surge bin/vertical elevator, auger/divider/strike off blade, and screed assembly. New asphalt is delivered from the hot mix plant by highway dump trucks and discharged into the Recycling Machine""s hopper. The Recycling Machine""s on-board computer meters the new asphalt (stored in the hopper) proportionally (approximately 10% to 15% by weight of the asphalt being 100% recycled) on to the central belt conveyor. A hopper/diverter valve diverts the new asphalt into the surge bin""s vertical elevator. The vertical elevator is positioned in the 100% processed asphalt""s windrow to continuously pickup asphalt. The processed asphalt and the metered, new asphalt are blended at the vertical elevator and delivered to the surge bin. The new asphalt may also be diverted directly on to the 100% recycled asphalt (windrow) exiting the pug mill.
3. 100% HIR (Integral Overlay): In this application, the old asphalt pavement is heated by a plurality of Preheaters to soften the asphalt for processing by the Recycling Machine. The final Preheater may be fitted with carbide cutters, asphalt collection blades (rake assembly) and an aggregate distribution system. The Recycling Machine is equipped with a front asphalt hopper/variable speed chain slat conveyor, truck pusher bar, variable speed central conveyor, shuttle conveyor, primary asphalt distribution auger/divider/strike off blade, secondary asphalt distribution auger and primary/secondary screed assemblies. New asphalt is delivered from the hot mix plant by highway dump trucks and discharged into the Recycling Machine""s front hopper. The Recycling Machine""s mills, pug mill, primary auger/divider/strike off blade and screed assembly, process and place the 100% recycled asphalt. The Recycling Machine""s on-board computer meters the new asphalt (stored in a hopper) via the central conveyor and shuttle conveyor to the secondary asphalt auger and screed assembly and if required, to the primary auger/divider/strike off blade and primary screed assembly. The new asphalt is placed by the secondary screed assembly on top of the 100% recycled asphalt (being laid to grade by the primary screed assembly) resulting in a hot, thermal bonding between the two layers. The 100% recycled and new asphalt is not mixed together, as in the Remix method. Both the primary and the secondary screed assemblies feature a novel grade control system used to place the asphalt to grade while also controlling the depth differential (generally 0.5 to 1 inch) of the asphalt laid between the two screed assemblies.
A standard, asphalt-paving machine used in the industry is designed to lay hot, plant mix asphalt delivered from the asphalt plant by dump trucks. The paving machines are either rubber tire or track driven machines. Neither type has any hydraulic suspension to raise and lower the paving machine""s mainframe. The asphalt is generally dumped into the front hopper of the paving machine where it is conveyed rewards by two, independently controlled, slat conveyors. The conveyed asphalt drops into two, independently driven, variable speed, hydraulically driven augers. The left auger receives asphalt from the left conveyor and the right auger from the right conveyor. The augers convey asphalt out from the center of the paving machine to the ends of the screed""s extensions. Electronic level sensors are attached to the ends of the left and right side extension screeds to control the speed of the independently driven augers and conveyors. If the level of asphalt drops in one or both of the extension screeds, the auger(s) and conveyor(s) will increase in speed, delivering more asphalt. The level of asphalt (head of material) should be maintained across the complete width of the screed assembly. Generally the asphalt will be to the height of the auger""s drive shafts (half full) with the augers slowly turning (without stopping) while conveying asphalt to the screed""s extensions. Behind the two augers is the screed assembly, which is responsible for spreading (laying) the hot asphalt to a specific depth and grade. The screed assembly consists of the main screed and a left and right extension screed. The main screed is fixed in width while the extension screeds can be hydraulically extended or retracted as the paving machine is operating, thereby altering the paving width. The screed is attached to the paving machine""s mainframe by screed tow arms that reach forward to behind the front hopper. The screed tow arms are attached to the paving machine""s mainframe by the left and right side tow points. The tow points can be pinned into position for manual control. A skilled operator uses crank handles at either side of the screed to adjust the screed""s angle of attack. The screed allows more asphalt to flow under its plate (screed rises) when its angle of attack is increased (front of the screed plate is higher than the rear) and visa versa. For automated control of the screed, the left and right crank handles are locked into position. Hydraulically raising or lowering the screed arm""s tow points controls the screed""s angle of attack. Raising a tow point will increase the angle of attack and visa versa. The automatic grade control sensors that control the tow points are mounted to the rigid tow arms and sense the asphalt""s grade using averaging beams, joint matcher, string lines or a non-contact, sonic sensor beams. The averaging beams and the joint matcher make physical contact with the asphalt""s surface and are towed by the paving machine, generally one on either side. The string line is a long string or wire that is erected using surveying equipment. The paving machine uses the string line as a fixed, reference grade. The mounting position of the sensors can be adjusted (distance from the tow point) to control the response of the system. Generally the screed""s reaction to grade deviations needs to be slow to produce a smooth riding, asphalt surface. The sensors should be mounted closer to the tow point to achieve a slow, smooth reaction. Mounting the sensor closer to the screed""s pivot point (away from the tow point) speeds up the reaction time and is better suited to joint matching applications. For surfaces where the right hand averaging beam cannot practically be used due to obstructions, poorly graded shoulders, curbs, etc., an electronic slope sensor, attached to the main screed can be substituted in place of the right averaging beam and sensor. The slope sensor allows the percentage of grade to be electronically adjusted while the paving machine is processing. For accurate grade and slope control Topcon""s Paver System Four or Five together with their Smoothtrack(copyright) 4 Sonic Tracker II(trademark) averaging beams are highly recommend. Attached to each of the screed""s tow arms is an aluminum beam fitted with four (non-contacting) sonic sensors that electronically average the surface""s grade. Topcon""s electronic Slope Sensor is mounted to the screed assembly. The Sonic Trackers and the Slope Sensor work together to determine the screed""s position relative to the desired grade and generate correction signals that are used by the Recycling Machine""s on-board computer to hydraulically control the screed arm""s tow points. To produce a quality, asphalt surface that meets all engineering specifications requires considerable operator skill, knowledge and equipment capable of properly performing the work. Consistency is one of the keys when producing a quality; asphalt surface and the following major points should be followed when laying new asphalt with a paving machine or 100% recycled asphalt with a recycling machine with attached screed(s):
a. Processing should be continuous with no stops. Stopping the screed assembly allows it to settle into the hot asphalt, causing depressions. Stopping for too long a period causes the asphalt in front of the screed assembly to cool, resulting in the screed assembly rising when forward travel is resumed.
b. The processing speed should remain as consistent as possible. An increase in speed will cause the screed assembly to rise while a decrease will cause the screed assembly to sink.
c. The temperature of the asphalt in front of the screed assembly (head) should remain consistent. If the temperature drops the screed assembly will rise and visa versa.
d. The asphalt in front of the screed assembly should remain at a consistent level, across the complete width of the main screed and the screed""s extensions. An increase in asphalt level will cause to screed assembly to rise while a decrease will cause it to sink.
The cold planer (milling machine or grinder) is generally a heavy, high-powered machine fitted with a large diameter, cutting drum. Attached to the cutting drum are replaceable carbide teeth and holders. The cold planer is designed to mill to grade, asphalt and concrete surfaces. The carbide cutters are generally sprayed with water, which is used for cooling and dust control. The milling drum discharges the milled product on to a high capacity, rubber conveyor belt that delivers the material to a fleet of waiting dump trucks to be hauled away. The cutting drum""s depth of cut (width is fixed) is manually or automatically controlled. Automatic grade control is generally accomplished by using the same sensors as the paving machine; however, long averaging beams are not generally used. More common, is the fixed string line, single sonic sensor on each side or Topcon""s Smoothtrack(copyright) 4 Sonic Tracker II(trademark) averaging beam on each side. The automatic grade control sensors on the cold planer automatically control the cutting drum""s depth by raising or lowering the machine""s mainframe to which the drum is attached. Three or four hydraulically activated legs (struts) are fitted with hydraulically driven tracks are used to propel the machine. The struts also turn to provide steering and raise and lower to provide the necessary grade control. The automatic grade control sensors that control the struts are mounted to the mainframe (generally close to the centerline of the cutting drum) and sense the asphalt""s grade using left and right side sonic sensors. For surfaces where the right hand sensor cannot practically be used due to obstructions, poorly graded shoulders, curbs, etc., an electronic or hydraulic slope sensor, attached to the mainframe can be substituted in place of the right sensor. The slope sensor allows the grade (percentage) to be electronically adjusted while the planing machine is milling material.
Prior 100% HIR recycling machines have systems designed to process and lay 100% recycled asphalt to grade using a standard, asphalt-paving screed. Recycling machines fitted with an attached screed have had major problems with the varying amount of processed, recycled asphalt, which collects in front of the screed assembly, especially when milling to grade (averaging the high and low areas). Milling to grade causes the volume of recycled asphalt to vary as high and low areas of pavement are milled. High sections increase the amount of asphalt being processed, while low sections require supplemental asphalt, to make up any deficiency. The only way, until now, that the amount of asphalt in front of the screed assembly could be controlled was by manually increasing the angle of attack (raising) of the screed assembly to release excess asphalt, or reduce the angle of attack (lowering) to collect asphalt. Manual, operator adjustment of the screed assembly generally results in bumps and an inconsistent grade of the finished asphalt surface (mat). Others have tried to resolve the problem by removing the screed assembly from the recycling machine. The recycling machine (less screed) either conveys the heated, recycled asphalt into a standard paving machine positioned under the rear of the recycling machine, or leaves a windrow of hot asphalt on the milled asphalt""s surface, which is picked up by a windrow conveyor attached to the paving machine. The front hopper of the paving machine stores any excess asphalt when not required by the screed assembly.
The following problems arise when the screed assembly is removed from the recycling machine:
a. Increased costs: A paving machine and windrow conveyor must be purchased and operated in addition to the recycling machine. Shipping both units requires a trailer as the units are not self transportable.
b. Reduced asphalt temperature: The temperature of the recycled asphalt contained in the windrow drops the further the windrow conveyor and paving machine are positioned from the recycling machine. Heat is also lost at the windrow conveyor and paving machine as the hot asphalt is handled. Low asphalt temperatures cause the screed assembly to tare the mat (open surface). This also causes a problem with final mat compaction during rolling. Asphalt meeting Superpave specifications generally requires higher temperatures to be maintained behind the screed assembly with the steel drum roller operating as close to the screed assembly as practicably possible.
c. Increased segregation: Hot asphalt should always be moved as a mass to prevent segregation. The windrow conveyor and paving machine increase the handling operations of the hot asphalt, causing the larger aggregate to separate (segregate) and tumble to the sides, causing marks in the finished mat. Asphalt meeting Superpave specifications generally uses a larger size aggregate than conventional asphalt. Segregation will become a greater problem with the larger aggregates.
d. Increased pollution and increased equipment train length: The windrow conveyor opens up the hot, asphalt windrow as the asphalt is conveyed upwards into the paving machine""s front hopper. Excessive smoke (natural byproduct of hot asphalt) is produced (if the asphalt is at the correct temperature) causing a problem to the paving machine""s operators. Asphalt meeting Superpave specifications will cause even greater problems with smoke due to the higher temperatures.
e. Safety: Safety is an issue when processing with an open windrow. It is quite common for automobiles to try and cross the heated windrow, only to become stuck in 200 to 300+ Deg F. asphalt. Animals have seriously burnt their feet, as have humans with open footwear! Recycling machines with an attached screed assembly do not suffer from the above problems, as there is no open windrow.
The following problems have, until now, prevented current 100% HIR systems and machines from producing quality, recycled asphalt that meets pre-engineered specifications:
1. Inconsistent heating of the asphalt pavement to the proper depth required for 100% HIR.
2. Inconsistent smoothness when milling with 100% HIR machines.
3. Inconsistent smoothness and surface defects, caused by asphalt handling problems when using an attached screed assembly using 100% HIR machines.
4. Inconsistent ratio of new asphalt to 100% recycled asphalt when using the Remix method.
5. Inability to process asphalt around utility structures and obstructions.
6. Inaccurate and inconsistent application of liquid additives.
7. Inaccurate and inconsistent application of additional aggregate.
8. Improper mixing of rejuvenator fluid, washed aggregate and reworked asphalt.
9. Inability to remove moisture from the reworked asphalt.
10. Inconsistent depth differential between the 100% recycled asphalt and the new asphalt when using the Integral Overlay method.
The present invention solves the above-mentioned problems.
1. Inconsistent heating of the asphalt pavement to the proper depth required for 100% HIR
A critical step in the 100% HIR of asphalt pavement is getting the heat down into the asphalt to a depth (2xe2x80x3 or more) that will produce an average temperature that is hot enough to properly process the asphalt, without damaging the asphalt. Experience has shown that different mixes of asphalt absorb heat at different rates. For instance, asphalt with the addition of steel mill slag absorbs heat at a much different rate than asphalt with the addition of asbestos or rubber. The amount of moisture contained in the asphalt also plays an important part in the way that heat is absorbed with high percentages reducing the heating efficiency. When asphalt is not heated to sufficient depth, the following problems will occur:
The milling equipment will fracture the aggregate (stone) in the asphalt, degrading the asphalt""s physical structure.
Insufficient moisture will not be driven out of the asphalt, in the form of steam, preventing the proper coverage and bonding of liquid additives to the asphalt""s aggregate.
The effective mixing of additives (aggregate and rejuvenator fluid) will be reduced due to the asphalt not flowing correctly in the mills and pug mill.
The screed assembly will tear the finished mat due to low asphalt temperatures.
If the asphalt is over heated (generally the top surface) and the heat does not penetrate to the required depth, the following problems will occur:
The surface of the asphalt will be chard (burnt), causing degradation of the asphalt""s asphalt cement (AC) content and high levels of pollution, caused by fire and smoke.
The added rejuvenator fluid and polymer liquids will be degraded when they make contact with the overheated asphalt as the light fluid fractions will flash off (evaporate).
If the asphalt is inconsistently heated, to a sufficient depth, all of the above problems will occur, plus the screed assembly will sink and climb with the change in the asphalt""s temperature. Cold asphalt will make the screed climb (raise) while overheated asphalt will cause the screed to sink. Both conditions will cause grade and surface smoothness problems.
It can be seen that the temperature of the asphalt is critical to the 100% HIR process.
The present invention is able to maintain a consistent temperature through the use of, among other things, a temperature sensor in the pug mill which is designed to measure the final temperature of the asphalt leaving the pug mill (windrow). In addition, the pug mill""s discharge (100% recycled asphalt) is formed into a lightly compacted windrow by a parallelogram ski that measures the volume and temperature of the asphalt. An on-board computer monitors the windrow""s temperature and makes small adjustments to the forward processing speed, set by the operator. A decrease in the asphalt""s temperature will cause a slight decrease in forward processing speed, allowing the Recycling Machine""s (and the Preheaters) heater boxes greater time to heat the asphalt to the required depth. An increase in the asphalt""s temperature will cause a slight increase in forward processing speed, allowing the Recycling Machine""s heater box less time to heat the asphalt surface. The final temperature (pug mill discharge) of the 100% recycled asphalt will be fairly consistent, as the on-board computers attached to the three or more Preheaters and the Recycling Machine automatically monitor and control the complete heating process.
For manual operation, (each Preheater under its own on-board computer control) the Preheaters are equipped with electronic ground speed and asphalt, surface temperature monitoring and control. Each Preheater is set to track a preset (asphalt surface) heat range. The Preheaters and the Recycling Machine, monitor the temperature before, during and after the heater boxes. The Preheater""s front and rear heat sensors measure the asphalt surface""s heat differential, across the heater box and control the amount of heat by turning on and off the individual, electronically controlled burners. Heat sensors in each burner monitor and control each individual burner, while flame detectors shut down burners when flame (caused by crack filler or painted lines) is detected.
The Preheaters and the Recycling Machine may also be linked by wireless control (Ethernet). Satellite communication may also be used to replace the wireless control system. Each machine may also be fitted with a satellite Global Positioning System (GPS). The Recycling Machine and Preheater""s on-board GPS computers will allow all of the machines to self steer and maintain the correct spacing (in relation to the Recycling Machine) for proper heat transfer to the asphalt. Data for the on-board GPS computers will be determined by a pickup truck, fitted with a mechanical, center lane guide and GPS sensor(s) positioned at the center of the truck. Two sensors will be used to provide greater accuracy. The pickup truck will be driven down the road (mechanical center lane guide positioned over center of road) prior to processing, with the GPS sensors readings being recorded into a portable computer fitted with a removable disk or a memory card (Zip or flash). The data will be downloaded into all of the machine""s on-board computers. The truck can also be equipped with a metal detection boom with left and right side, hydraulically operated extension booms. A series of metal detectors are attached to the booms and detect iron utility structures in the asphalt""s surface. The extension booms are hydraulically moved in and out to follow the width of the asphalt surface to be recycled. Electronic position sensors (LVDT) measure the position of the boom""s extensions. The GPS computer records and stores the location of all iron structures. The Recycling Machine and the Preheaters will also be fitted with GPS sensors. The sensors may be fitted to the front and the rear of Recycling Machine and the Preheaters. The on-board computers compare the machine""s actual position, to the stored position, recorded by the pickup truck""s sensors. The on-board, computers monitor the Preheater""s spacing and monitors and controls the steering (front and rear) when the automatic steering mode is selected. All GPS equipped machines are programmed to steer accurately down the center of the lane, not the center of the road. The Recycling Machine""s processing width can be varied, while in operation, therefore the operators can process varying lane widths on both sides of machine. For safety reasons the machine operators can override the GPS control system at any time.
For large areas or straight-line work, a laser beam can be used to automatically guide (self-steer) the pickup truck in a straight line. Once the data has been stored to disk or memory and downloaded in to each machine""s on-board computer, each pass is programmed at a selected width from the last pass. It is also possible to use the on-board GPS system fitted to each machine to program the coordinates directly, rather than using the data obtained by the pickup truck GPS system.
The GPS""s metal detection readings are used by the final Preheater (unit ahead of the Recycling Machine) and the Recycling Machine""s GPS and on-board computers to automatically raise and lower the rake/blades assemblies, extension mills, main mill and the pug mill, preventing damage to the sub-assemblies and iron utility structures. All machines fitted with the GPS system will also be equipped with sonic sensors mounted at the front of the machines. An operator warning horn will sound if an obstruction, such as an automobile is detected. The machine is programmed to stop when a minimum distance is reached.
The wireless data transmission will allow all of the machines to communicate with each other, providing accurate and efficient heating.
The system can be designed to operate under the following parameters:
All Preheaters and the Recycling Machine will be under their own control until processing speed and control has been established and stabilized.
The Recycling Machine (master) will control the spacing of the Preheaters (slaves) using wireless, GPS or satellite control.
The lead Preheater will produce as much heat as possible without damaging the asphalt""s surface.
All other Preheaters following the lead Preheater will regulate their heat output based upon the temperature of the asphalt""s surface ahead and behind (heat differential) their heating elements (boxes). Each Preheater is designed to produce as much heat as possible without damaging the asphalt""s surface.
The final Preheater is equipped with a rake scarification/blade collection system and aggregate distribution bin, controlled by the Preheater""s on-board computer. The aggregate bin must be occasionally filled with aggregate by a wheel loader. Space must be provided not only for the wheel loader, but also for the dump trucks discharging asphalt into the front hopper of the Recycling Machine. This necessitates the final Preheater being controlled by the operator (taken out of automatic control). All of the Preheaters ahead of the final Preheater will automatically move ahead once the final Preheater has reached a preset distance from the Preheater ahead (positions monitored by the on-board GPS systems). As the Preheaters move ahead their heating output will automatically increase (if possible) due to the increase in the heat differential across their heating elements (boxes). Once the aggregate bin has been filled or the dump truck has been released, the final Preheater is returned to automatic control. All of the Preheaters will slow down, allowing the Recycling Machine to catch up. The heating output of the Preheaters is automatically reduced during the catch up period due to the decrease in the heat differential across their heating elements (boxes), thereby preventing overheating of the asphalt.
The Recycling Machines heating system is designed to fine-tune the asphalt""s final temperature before the asphalt is processed by the rake scarification and milling systems. The heating system is programmed to operate at 50% or less of its heating capacity (50% or less of the electronically controlled burners on the main heater box turned on). When the final Preheater is fitted with a rake scarification/blade collection system and aggregate bin the Recycling Machine""s heating system must produce enough heat to remove any remaining moisture in the aggregate without degrading the asphalt. The scarifying process breaks the asphalt""s surface, limiting the amount of heat that can be applied. The average temperature of the heating system can be set and controlled by the on-board computer. Individual, electronic burners will maintain this average by regulating their heat output. Infrared sensors monitor the asphalt""s temperature, ahead of the heating system. The mill""s grade control shoes (located behind the heating system) are fitted with heat thermocouples that monitor the temperature of the asphalt""s surface, ahead of the rakes and mill assemblies. This temperature information, together with the pug mill""s discharge (windrow) temperature and the operator""s input for the base processing speed, controls the actual processing speed of the Recycling Machine. For instance, the operator has set the base_processing speed to 20 feet per minute, based upon information displayed upon his monitor (screen). The on-board computer is programmed to monitor key operating parameters such as Preheater/Recycling Machine""s asphalt processing temperature differentials and the Recycling Machine""s engine percentage load factor and will display a recommended base processing speed. The temperature of the asphalt in the windrow has been programmed at a set point of 320xc2x0 F. The thermocouples on the grade shoes are reading 550xc2x0 F. and the heating system is operating at 50% of its output. As the windrow temperature increases to 325xc2x0 F. and the mill""s grade shoes average temperature increases to 560xc2x0 F. the Recycling Machine""s actual processing speed increases automatically. The Recycling Machine""s on-board computer will also send information by wireless or GPS to all of the Preheater""s on-board computers to speed up their forward travel speed. When the Preheaters are at 100% of their heating capacity and the temperature differential across their heating systems begins to increase to a preset, set point, it signals that the train is getting to the point of going too fast for the asphalt to properly absorb heat. The Recycling Machine""s on-board computer monitors all of the Preheater""s temperature differentials (via wireless or satellite link) and will start to slow down its processing speed and the Preheaters, allowing more time for the asphalt to absorb the heat. The infrared temperature sensors in front of the Recycling Machine""s heater box can instantly turn the heating system up to 100% capacity if the asphalt""s temperature reaches a preset minimum set point. This can occur when the final Preheater""s aggregate distribution system deposits a higher percentage of aggregate when its grade profiling system traverses a high section in the asphalt""s surface. The increased volume of aggregate (generally washed, damp sand is used to modify the asphalt""s air void ratio) will reduce the asphalt""s surface temperature and the extra heat will be required to drive out the excess moisture and bring the aggregate up to the proper temperature. The temperature drop could also be the result of the Preheater""s rake scarification/blade collection system (set to scarify at 2 inches or more) releasing large quantities of moisture (steam) out of the heated asphalt. The Recycling Machine""s heating system is designed to operate at 100% of its heating output (all of the electronically controlled burners turned on), once the processing speed reaches a pre-set limit (around 22 feet per minute). 100% heating capacity is also used if the asphalt""s temperature at the rear of the final Preheater heating system suddenly drops to a minimum temperature, set point when operating at below 22 feet per minute. If the temperature behind the final Preheater does not return to its normal operating temperature range within 10 feet, the Recycling Machine""s on-board computer (using data obtained from the final Preheater by wireless or satellite transmission) will slow the Recycling Machine and Preheaters down using the GPS. This electronic monitoring, transmission and control loop is continuously repeated, providing maximum heating efficiency and processing speed.
2. Inconsistent smoothness when milling with 100% HIR machines:
The accuracy of the milled surface (grade) and the accurate placement of asphalt on to the milled surface determine the smoothness of the compacted, asphalt mat. If either one is incorrect the riding quality (smoothness) will be reduced. The present invention is fitted with two types of on-board, computer controlled, automatic grade control systems that monitor pavement grade to automatically control all of the milling and screed assembly operations:
a. Full, mainframe grade control: For asphalt surfaces requiring the accurate milling and placement of asphalt (highway and airport runways) a novel grade and slope control system has been developed. When using full, mainframe grade control, the mills and screed arm tow points are mechanically, electronically or hydraulically locked to the grade of the Recycling Machine""s mainframe. The system can utilize Topcon""s Paver System Four or Five together with their Smoothtrack(copyright) 4 Sonic Tracker II(trademark) (non-contact) averaging beam(s) or mechanical averaging beam(s) on one or both sides of the Recycling Machine""s rear end. All of the mechanical averaging beams are attached and towed by the Recycling Machine""s mainframe while Topcon""s Smoothtrack(copyright) 4 Sonic Tracker II(trademark) averaging beam(s) are fixed to the mainframe as they do not have to be towed. All of the beams longitudinal track the asphalt""s surface. The longer the beam the greater the averaging effect. Topcon""s Smoothtrack(copyright) 4 Sonic Tracker II(trademark) averaging beams are preferred as they do not make contact with the asphalt""s surface, thereby eliminating marking (scuffing) of the previously finished mat and can also be used on the curb side (right) of the Recycling Machine. They also provide increased accuracy and easier setup/operation. The mechanical averaging beams use electrical or hydraulic sensors (attached to the Recycling Machine""s rigid main frame) to sense the grade (position) of the beam. Wands or arms attached to the sensors make physical contact with the beams or travelling string line (string line attached to the beam). Whichever sensor system is used, the Recycling Machine""s grade (mainframe) is controlled as explained in the following example. The Recycling Machine""s rear, left side axle and mainframe begin to sink (lower) in grade, compared to the left side averaging beam""s grade (the Recycling Machines right side grade remains on grade). The grade control system will signal for hydraulic oil to be sent to the left, rear axle""s, hydraulic leveling cylinder (attached between the mainframe and the rear axle assembly). The left hydraulic cylinder extends and tilts the mainframe, keeping the mainframe on grade. The electronic or hydraulic sensor automatically stops the hydraulic oil supply to the left hydraulic cylinder as the mainframe is raised back to match the averaging beam""s grade. The grade of the frame has to change to produce input into the sensors; however, this change in grade is small and has little or no effect on the final grade of the asphalt""s surface. The right hydraulic leveling cylinder is under the control of the right averaging beam and sensor. For surfaces where the right hand, mechanical averaging beam cannot practically be used due to obstructions, poorly graded shoulders, curbs, etc., the electronic slope sensor (located at the rear end of the Recycling Machine""s mainframe) can be substituted in place of the right averaging beam and sensor. The slope sensor allows the percentage of grade to be electronically adjusted while the Recycling Machine is processing. Topcon""s Smoothtrack(copyright) 4 Sonic Tracker II(trademark) averaging beams together with Topcon""s frame mounted electronic slope sensor allow averaging on both sides or cross slope to be specified. To allow the above grade and slope control system to operate the Recycling Machine is designed with a hydraulic, three-point suspension system that lifts and lowers both ends of the Recycling Machine""s mainframe as well as tilting it. Two hydraulic cylinders per axle assembly are attached between the mainframe and front and rear axle assemblies. The two front cylinders (front axle assembly) are hydraulically connected in parallel, while the rear axle""s hydraulic cylinders are individually controlled, thus forming a three-point suspension system. The front and rear axle assemblies are fitted with hydraulic wheel motors and rubber tires, inflated with dry nitrogen to high pressures to prevent the tire""s side walls from deflecting which would have a negative effect on grade control. Both axle assemblies can steer 40 degrees in both directions, providing accurate steering. The rear tires contact the heated asphalt""s surface, milled by the main and extension mills (located ahead of the rear axle). The front axle assembly follows the original, heated asphalt""s surface and is free to oscillate when working on uneven surfaces. Grade changes will cause the front axle assembly and to some degree the front of the mainframe to rise and fall, however, this has little effect on the rear end of the mainframe due to the frame""s long length. As noted above, input from the left and/or right side averaging beams or the left side averaging beam and electronic slope sensor are used to control the operation of the two individual hydraulic cylinders attached between the rear of the mainframe and the rear axle assembly. The Recycling Machine""s mainframe is said to be xe2x80x9clocked to gradexe2x80x9d by the sensors. The extension mills and the main mill are raised and lowered in relation to the mainframe by four, individual (left and right) hydraulically operated sliding struts, controlled by four automatic grade control sensors. When utilizing full, mainframe, grade sensing, the mills automatic grade control sensors sense the mainframe""s position. Fine adjustments can be made to the depth of cut by adjusting each, individual sensor. This is desirable when setting the cutting depth between the extension mills and the main mill. The screed arm""s tow points can be locked mechanically (pinned) to the mainframe.
The screed is attached to the screed tow points (left and right side of the recycling machine) by pivoting, rigid arms. The tow points can be pinned into position for manual control by a skilled operator who uses crank handles at either side of the screed assembly to adjust the screed""s angle of attack. The screed assembly allows more asphalt to flow under its plates (screed assembly rises) when its angle of attack is increased (front of the screed""s plates higher than the rear) and visa versa. For automated control of the screed assembly, the left and right crank handles are locked into position. Hydraulically raising or lowering the tow points controls the screed assembly angle of attack. Raising a tow point will increase the angle of attack and visa versa. The automatic grade control sensors that control the tow points are mounted to the rigid screed arms and sense the asphalt""s grade using Topcon""s Smoothtrack(copyright) 4 Sonic Tracker II(trademark) averaging beams, mechanical averaging beam(s), joint matcher or string lines. The mounting position of the sensors can be adjusted (distance from the tow point) to control the response of the system. When the mechanical averaging beams (towed) are used the screed arm""s sensors, sense of the same averaging beams used by the Recycling Machine""s mainframe grade control sensors. The right hand, screed tow point can be controlled by using a second electronic slope control, attached to the screed. Generally the mainframe and the screed assembly would both be operating with individual, electronic slope controllers. A major advantage of using the automatic grade controls to control the screed assembly tow points (even though the mainframe is locked to grade already) is due to the influence of varying, asphalt levels (in front of the screed assembly), travel speed, asphalt density and heat. Example: If the Recycling Machine is (fitted with mechanical averaging beams on both sides) slowed for traffic, the screed assembly will tend to sink (less asphalt flow under the screed plates) whereas the mainframe will remain at grade as the rear axle""s wheels are tracking a solid, milled asphalt surface. The automatic grade sensors mounted on the screed""s tow arms will sink with the screed assembly, however, the mechanical averaging beam""s grade remains consistent. As the sensors sink they signal and control the hydraulic oil flow into the tow point""s cylinders, raising the tow points, which increases the screed assemblies angle of attack, resulting in a consistent grade. Other recycling machines have manual adjustments on the mills for depth control or have automatic grade controls fitted to the mills with very short skis or pans. The problem with both systems is in following the original, uneven surface grade causes the mills to profile to the original grade, rather than averaging the grade as in the case of the long averaging beams. For example: A utility trench, stretching transversely across the complete width of the asphalt pavement has settled (depression) by 2 inches. The short grade skis or pans attached to the mills will follow in and out of the depression causing the mills to cut to the same profile. This depression will show up in the finished mat as a depression, after final rolling. The long averaging skies, by comparison, would hardly notice the same depression. Finally, if the milled grade is continuously varying (up and down) then the recycling machine""s and/or the paving machine""s wheels or tracks are following the undulating grade, causing their automatic grade controls to work harder while controlling the screed assembly grade. It is interesting to note that the grade of the asphalt being laid by any screed assembly, if the automatic grade controls are set properly, will remain very consistent, even with an undulating, milled base surface. However, during final compaction of the asphalt by the rollers, the finished mat will follow, to a degree, the profile of the undulating, milled base surface, thereby producing a mat with poor smoothness characteristics.
b. Left and right side averaging skies for the extension mills and the main mill: For secondary roads, city streets and asphalt surfaces where full, mainframe grade averaging is not practicable using long, mechanical averaging beams, the recycling machine is equipped with left and right side skis, or optional, averaging skis. The skis are located ahead of the extension and main mills. The two averaging ski assemblies contact the heated, unprocessed asphalt (original grade) and are manually adjustable in width, allowing setup for various processing widths. The extension mills (left and right side) are hydraulically adjustable in width and crown while the main mill, located behind the extension mills is of fixed width. The left ski automatically controls the grade (depth of cut) of the left extension mill and the left side of the main mill. The right ski controls the grade of the right extension mill and right side of the main mill. The left and right ski assemblies are connected by a jointed, cross beam to which various attachments, used to contact the heated asphalt surface, can be added. In its simplest form, two sliding shoes (the shoes contact the heated surface) are mounted to the cross beam and follow the profile of the asphalt""s surface, generally in the wheel ruts created by traffic, as this is generally the smoothest part of the surface on badly rutted asphalt. In its most complex form two sets of shoes (one on either side of the Recycling Machine) are attached to the cross beam by pivoting beams, allowing the transverse surface across the asphalt to be averaged. Left and right extension beams are attached (when space permits) to the jointed, cross beam, allowing the shoes to reference the surface to the left and right of the Recycling Machine. The left side shoe(s) can be replaced by wheels attached to averaging beams, running in line (longitudinally) with the Recycling Machine and on the asphalt surface processed on the previous pass. The wheels are used to prevent marking of the previously finished mat. This allows the mills to profile to the grade of the previously finished surface. Shoes can also be used if wheels are not required. The mill""s grade control system can transversely or longitudinally average the asphalt surface, providing far greater accuracy than simple, shorts shoe sensors, mounted directly on to the extension and/or main mill. The left and right side of the grade control cross beam are attached by two pivoting links to the left and right side, sensor control stations that house the hydraulic (electronic are optional) grade control sensors. The left, sensor control station controls the left extension mill and left side of the main mill, while the right, sensor control station controls the right side of the mills. Both the extension mills and main mill are raised and lowered by four (two for the extension mills, two for the main mill) hydraulically operated, sliding struts attached to the machine""s mainframe. The sliding struts on the extension mills attached between the Recycling Machine""s mainframe and the extension mill""s mainframe. The left and right side extension mills are attached to the extension mill""s mainframe by hydraulic cylinders, allowing the extension mills to pivot (crown), independently to the extension mill mainframe. The sliding struts for the main mill attach directly to the main mill""s mainframe. Attached to each sliding strut is a manually adjustable height screw, which the grade control sensors touch (sense). Each grade control sensor (attached to the sensor control station) monitors the position of the height screws. The following example will explain the operation of grade correction for the right hand side. The Recycling Machine is entering an intersection with a raised section of asphalt pavement. The right hand averaging shoes (in contact with the heated asphalt surface) begins to rise, causing the sensor control station to rise. The two right hand, grade control sensors (attached to the sensor control station), move away from the sliding strut adjuster screws and supplies hydraulic oil to the hydraulic cylinders attached between the mainframe and the sliding struts. The sliding struts are automatically raised, moving the adjuster screws up to match the position of the sensor control station, cutting of the supply of hydraulic oil. The sliding struts/adjuster screws will always follow the position of the sensor control stations. Manual adjustment is provided to allow for fine adjustments to each individual strut to fine tune the milling height between the extensions and the main mill. Manually crowning of the left and right extension mill by the operator is possible without effecting the position of the sliding struts. This is desirable when working in city streets with poor grade, intersections, driveways and irregular curbs and/gutters. With this grade control system with both mills sensing the sensor control stations, any sliding strut can be manually raised or lowered, without effecting the other sensors. The left and right sensor control stations are mounted to the Recycling Machine""s mainframe by a parallelogram linkage, which raises and lowers the grade control sensors in absolute alignment with the sliding struts. The sensor control stations are also attached to the mainframe by a hydraulic lift/damper cylinder. The function of the hydraulic lift/damper cylinder is to carry a percentage of the sensor control station, beam and averaging shoe""s weight, preventing the shoes from sinking into the hot asphalt. The hydraulic lift/damper cylinder is also responsible for dampening the mechanical action of the grade system by restricting oil flow. The sensor control stations also incorporate flat springs for connection between the jointed, cross beam. The spring deflects if a sudden movement occurs as in the case of the shoes riding up and over a raised utility structure. The spring(s), working together with the hydraulic lift/damper cylinder prevent the sudden movement of the sensor control station(s), which in turn prevents the mills from suddenly raising, leaving a high section in the milled surface. The same applies if the shoes suddenly drop into a transverse depression, the spring deflects and the cylinder dampens. It is important to note that the rear wheels of the Recycling Machine follow the grade set by the main mill assembly.
3. Inconsistent smoothness and surface defects, caused by asphalt handling problems when using an attached screed using 100% HIR machines
As mentioned before (when discussing paving machines), producing a quality, asphalt surface that meets all engineering specifications requires considerable skill, knowledge and the proper equipment. Consistency is one of the keys, with the following innovations providing the consistency when 100% recycling with the Enviro-Pave Recycling Machine:
a. Processing should be continuous with no stops. Stopping the screed assembly allows it to settle into the asphalt, causing a depression. Weight transfer from the screed assembly to the Recycling Machine""s mainframe has been tried and found to work, however when forward travel was resumed the screed assembly would still tend to sink. Two hydraulic cylinders (attached between the mainframe and screed assembly) are used to raise and lower the screed assembly. When processing, the two hydraulic cylinders are floating (oil can freely flow in and out of both ends of the cylinders). When forward travel must be stopped the cylinder""s hydraulic float is cut off and oil is directed into one end of the cylinders (screed raise) at a pressure high enough to transfer weight from the screed assembly to the mainframe. Transferring weight prevents the heavy screed assembly from sinking into the mat. A time delay, controlled by the on-board computer has now been added, allowing the screed time to stabilize with asphalt flow as forward travel is resumed. This delay will be equal to one or more lengths of the screed""s main plate.
b. The processing speed should remain as consistent as possible. An increase in speed will cause the screed to rise while a decrease will cause the screed to sink. An optical encoder, mounted to one of the rear axle assembly drive motors will provides the equivalent of cruise control by monitoring the drive wheel""s RPM. The on-board computer will control the flow of hydraulic oil in the drive system to maintain a consistent speed. Varying loads on the Recycling Machine will have no effect on the processing speed.
c. The temperature of the asphalt in front of the screed (head) should remain consistent as noted in detail above.
d. The asphalt in front of the screed assembly should remain at a consistent level across the complete width of the screed and screed extensions. An increase in asphalt level will cause to screed to rise while a decrease will cause it to sink. Generally, recycling machines fitted with an attached screed assembly have had problems when the screed assembly carried too much asphalt. This resulted in the screed assembly becoming uncontrollable. It was also common for the screed operator to load the screed assembly with an excessive amount of asphalt as it gave a reserve of asphalt for when the screed""s extensions suddenly became low in asphalt due to poor asphalt flow from the auger assembly. Carrying too much asphalt with the screed assembly also allowed the asphalt to stop moving at the screed""s extensions, resulting in the asphalt losing temperature and sticking to the screed""s face. The cold asphalt caused quality problems in the finished mat, if and when it passed under the screed""s extensions.
The following innovations are designed to control the head (amount) and distribution of asphalt across the main screed and screed extensions while reducing material segregation:
A heated (automated heat control and propane burner) and insulated, asphalt surge bin and vertical elevator, located inside the rear end of the Recycling Machine""s mainframe, automatically stores and releases hot asphalt to maintain a constant volume (head) of material in front of the screed assembly. The surge bin and vertical elevator are connected to the Recycling Machine""s mainframe by two hydraulic cylinders. The surge bin discharges the stored, hot asphalt through two (left and right side), bottom discharging, rotary valves located above and in front of the auger/divider/strike off blade assembly, which is located in front of the screed assembly. The left rotary valve supplies the left auger while the right rotary valve supplies the right auger. An integral, vertical elevator picks up the excess, 100% recycled asphalt (not required by the screed assembly) from the windrow exiting the Recycling Machine""s pug mill (mixing chamber) and elevates it up the front face of the elevator into the surge bin, for storage. The Recycling Machine""s on-board computer automatically starts and stops the vertical elevator by measuring the pressure in the two hydraulic cylinders and the height of material exiting the pug mill by monitoring the pug mill""s volume sensing ski. The hydraulic pressure is proportional to the weight of the asphalt in the bin. The surge bin""s holding capacity is sufficient for continuous operation without having to add new asphalt and once full, provides enough stored asphalt for the start-up of the process before the Recycling Machine""s windrow is established. Attached to the front side of the vertical elevator is a small hopper/diverter valve that can receive new asphalt from the optional front asphalt hopper/drag conveyor and the central conveyor. The hydraulically operated diverter valve allows new asphalt to be elevated by the vertical elevator into the surge bin for storage, or be discharged on to the windrow as additional material. Projects requiring additional asphalt include, shoulder widening, modification to existing grade or surfaces with a shortage of existing asphalt. Diverting new asphalt to the surge bin allows the bin to be filled at the beginning of the daily shift. Once the bin is initially filled recycled asphalt can be collected from the windrow for the remaining shift. This not only provides new asphalt, but also provides control over the startup procedure. The Recycling Machine""s screed assembly is positioned over the asphalt""s surface at the start of the new joint (the end of the previous joint). The screed assembly is set on to two starter spacers and the screed""s cranks are nulled (neutralized) and set. The front asphalt hopper is filled with hot mix asphalt, delivered by truck from the asphalt plant. The variable speed drag chain conveyor (part of the front hopper) delivers the asphalt to the variable speed, central conveyor. The central conveyor (runs through the center of the machine) moves the asphalt to the hopper/diverter valve, attached to the surge bin""s, vertical elevator. Asphalt is diverted to the vertical elevator and the surge bin is automatically filled to the correct level by monitoring the hydraulic pressure in the two surge bin support cylinders. The augers and surge bin""s rotary valves are turned on to automatic, on-board computer control. The left and right augers will increase to maximum speed, as no asphalt is available to operate the two augers, electronic level sensors, located at the end of the screed""s extensions. The surge bin""s bottom discharging, rotary valves (left and right side) are automatically opened by sensing the speed of the individual augers, allowing asphalt to flow to the ends of the screed""s extensions and the auger""s electronic, level sensors. Once the screed""s extensions are full of asphalt, the augers automatically slow down and stop, while the surge bin""s rotary valves are automatically closed. As asphalt was flowing out of the surge bin""s rotary valves the on-board computer was automatically replenishing the surge bin to a full state. Once full the on-board computer automatically stops the elevator by measuring the surge bin""s hydraulic cylinders pressure. The hopper/diverter valve is fitted with an electronic sensor that controls the speed of the central conveyor. When the hopper is full the conveyor is stopped. Once the supply of asphalt to the screed assembly has been meet the Recycling Machine""s processing equipment is put into operation and the machine moves forward, preventing the screed from settling. Asphalt is now diverted from the vertical elevator to the asphalt""s surface to form a windrow of new material. As the diverter valve opens the electronic sensor detects the drop in the level of asphalt in the hopper/diverter valve and restarts the central conveyor and the front hopper""s drag chain. The central conveyor (in this case a belt conveyor) is fitted with an electronic belt scale, used to measure the weight of asphalt being conveyed. The on-board computer is programmed to supply the correct amount of asphalt to form a windrow by monitoring the individual speed of the auger. Gradually, as the pug mill""s discharge rate increase (greater volume of asphalt being processed), the on-board computer proportionally reduces the flow of new asphalt by monitoring the individual auger""s speed, measuring the volume of material exiting the pug mill""s, variable ski (asphalt volume measurement and the amount of weight on the conveyor belt""s scale. When 100% HIR recycling is being conducted and new asphalt is not required after the initial startup period, the front hopper, belt conveyor and the hopper/diverter valve can be emptied by discharging and blending the asphalt automatically into the asphalt surge bin. The vertical elevator picks up the 100% recycled asphalt from the windrow while the new asphalt (delivered from the front asphalt hopper) is blended in the vertical elevator, preventing variations in the finished mat""s surface texture. Generally the surge bin/vertical elevator are only required for 100% HIR once the process has been established. For asphalt surfaces requiring major grade corrections the front asphalt hopper and central conveyor can be used to automatically supplement and blend new asphalt into the process. In this case the on-board computer monitors the individual auger""s speeds, measures the volume of 100% recycled asphalt exiting the pug mill""s variable ski, the amount of weight on the conveyor belt""s scale and the amount of asphalt stored in the asphalt surge bin/vertical elevator. The on-board computer will maintain the asphalt surge bin""s level by scalping asphalt from the windrow, when processing volume is high and supplying new asphalt as processing volume decreases. An electronic temperature sensor monitors the new asphalt""s temperature on the central belt conveyor and automatically discharges the conveyor (into the asphalt surge bin/vertical elevator) when the temperature drops to a minimum value. This situation is possible when new asphalt is not required over longer periods of time (the asphalt""s grade has improved. The front asphalt hopper""s discharge remains shut off as the conveyor discharges. The on-board computer always leaves sufficient space in the asphalt surge bin for the volume of asphalt carried by the conveyor. Temperature sensors also measure the temperature of the asphalt stored in the front asphalt hopper assembly. The asphalt tends to drop at a slower rate as the front hopper has an insulated bottom and sides. Also the asphalt retains heat better when stored in bulk. The Recycling Machine operator is visually warned when the temperature drops to a level requiring action. If new asphalt is not available to supplement the existing asphalt in the front hopper the on-board computer will automatically discharge the hopper by slowly restarting the hopper""s discharge and the central belt conveyor, thereby delivering new asphalt to the rear hopper/diverter valve. The asphalt will be diverted to the heated windrow exiting the pug mill. The strike off blade, which is part of the auger/divider assembly, is designed to carry the excess amount of asphalt without effecting the operation of the screed assembly.
The screed auger/divide/strike off blade assembly, located in front of the screed assembly is responsible for conveying the heated asphalt windrow to all areas of the main screed and the screed extensions. The screed extensions (left and right side) are hydraulically extendable and are used to vary the paving width. The screed auger/divider/strike off blade assembly has two, independently controlled augers (left and right side) designed to split the hot, asphalt windrow and distribute asphalt to either end of the main screed and screed extensions. Individual auger speed is automatically controlled by industry standard, proportional, electronic level controls (paddles), located at either end of the screed""s extensions. As the asphalt level (head) drops at one or either end of the screed""s extensions the paddles signal the on-board computer to increase the auger(s) speed to convey more asphalt. As the asphalt is conveyed from the centrally located windrow the head of asphalt in front of the main/extension screed rises, raising the paddle(s) thereby slowing the auger(s). Generally both augers will be running at a continuous, slow speed, supplying a consistent flow of asphalt across the screed assembly. The screed auger/divider/strike off blade assembly can be hydraulically raised or lowered to adjust for varying depths of asphalt being process by the Recycling Machine. The operation of the screed auger assembly, described above, can be found on any paving machine and works well when laying thick lays of asphalt. It has not proved to be as successful when used with 100% HIR Recycling Machines laying 50 mm or less of recycled asphalt, particularly when working on slopes. Generally there has always been a problem splitting the asphalt windrow with just the screed auger assembly, especially when working on slopes. The high side of the screed extension (crown of the pavement) would generally be starved of asphalt. To overcome the problem the screed auger/divider/strike off blade assembly is fitted with a centrally mounted, hydraulically controlled, mechanical divider, designed to physically split the windrow and feed it into the left or the right auger (the auger requiring the greater amount of asphalt). The angle of the divider is controlled by the onboard computer and uses the left or right auger""s speed as a reference. As the auger(s) speed increases beyond a preset speed (level of asphalt dropping in front main screed and/or either screed extension) the on-board computer turns the hydraulic divider, diverting a greater percentage of the asphalt windrow into the auger requiring asphalt (the auger with the greatest speed). The position of the divider is electronically monitored, allowing the divider to turn proportionally to the individual auger""s speed. If both augers are rotating at the same speed the divider remains in the straight-ahead position. If the on-board computer determines that any auger""s speed is still increasing (divided windrow is not providing enough asphalt to the speeding auger) the rotary discharge valve of the asphalt surge bin, located above the speeding auger is automatically opened, providing additional, heated asphalt. The additional asphalt continues to flow from the asphalt surge bin until the auger slows to a predetermined speed, where upon the rotary discharge valve is automatically closed. If the on-board computer determines that the speed of both augers are too high (lack of asphalt in the windrow and at the screed assembly) both of the asphalt surge bin""s rotary valves are opened, thereby providing additional heated asphalt to both augers. The operation and control of the screed auger/divider/strike off blade assembly and the asphalt surge bin are designed to handle the heated asphalt in a slow and gentle manner so as to reduce segregation, heat loss and emissions. The asphalt surge bin automatically refills from the windrow when the volume of asphalt exceeds the volume required by the screed assembly, typically when milling through a high area of asphalt pavement. Attached to the front of the auger/divider is the manually adjustable strike off blades (left and right side). The blades functions as tunnels for the augers allowing asphalt to be conveyed more efficiently, without causing segregation. The strike of blades also limits the amount of asphalt that can physically reach the left and right side augers flights and also the screed assemblies front face. The two, strike off blades are adjustable in height and taper with the height of blades becoming greater towards the end of the augers, allowing more asphalt to flow under the blades towards the end of the augers. If a sudden surge of asphalt (highly unlikely due to the electronic control, larger asphalt surge bin and high capacity, vertical elevator) does occur when milling through a high section of asphalt, the auger/divider/strike off blade will carry the extra head of asphalt.
4. Inconsistent ratio of new asphalt to 100% recycled asphalt when using the remix method.
The general procedure used by other HIR recycling machines to introduce a percentage of new asphalt into the recycled asphalt (Remix) is to monitor the forward speed of the recycling machine. This procedure is not that desirable due to the fact that the volume of asphalt being recycled at any given time is constantly changing due to uneven surface grade and varying processing width, on variable width machines. The other problem is where the new asphalt is delivered for mixing with the recycled asphalt. which often results in the asphalt being dropped in front of the recycling machine""s heating system. The problem with this approach is that the new asphalt is subjected to unnecessary heat, which rapidly deteriorates the new asphalt.
The following innovations allow the present invention to provide a true ratio between the 100% recycled and new asphalt without degrading the new asphalt.
The present invention is equipped with a front asphalt hopper/variable speed chain slat conveyor, truck pusher bar, variable speed central belt conveyor and electronic belt scale, conveyor hopper/diverter valve, surge bin/vertical elevator, auger/divider/strike off blade and screed assembly. The Remix process starts by using the same method as the 100% HIR process. The Recycling Machine""s screed assembly is positioned over the asphalt""s surface at the start of the new joint (the end of the previous joint). The screed assembly is set on to two starter spacers and the screed""s cranks are nulled (neutralized) and set. The front asphalt hopper is filled with hot mix asphalt, delivered by track from the asphalt plant. The variable speed drag chain conveyor (part of the front hopper) delivers the asphalt to the variable speed, central conveyor. The central conveyor (runs through the center of the machine) moves the asphalt to the hopper/diverter valve, attached to the surge bin""s, vertical elevator. Asphalt is diverted to the vertical elevator and the surge bin is automatically filled to the correct level by monitoring the hydraulic pressure in the two surge bin support cylinders. The augers and surge bin""s rotary valves are turned on to automatic, on-board computer control. The left and right augers will increase to maximum speed, as no asphalt is available to operate the two augers, electronic level sensors, located at the end of the screed""s extensions. The surge bin""s bottom discharging, rotary valves (left and right side) are automatically opened by sensing the speed of the individual augers, allowing asphalt to flow to the ends of the screed""s extensions and the auger""s electronic, level sensors. Once the screed""s extensions are full of asphalt, the augers automatically slow down and stop, while the surge bin""s rotary valves are automatically closed. As asphalt was flowing out of the surge bin""s rotary valves the on-board computer was automatically replenishing the surge bin to a full state. Once full the on-board computer automatically stops the elevator by measuring the surge bin""s hydraulic cylinders pressure. The hopper/diverter valve is fitted with an electronic sensor that controls the speed of the central conveyor. When the hopper is full the conveyor is stopped. Once the supply of asphalt to the screed assembly has been meet the Recycling Machine""s processing equipment is put into operation and the machine moves forward, preventing the screed from settling. Asphalt is now diverted from the vertical elevator to the asphalt""s surface to form a windrow of new material. As the diverter valve opens the electronic sensor detects the drop in the level of asphalt in the hopper/diverter valve and restarts the central conveyor and the front hopper""s drag chain. The central conveyor (in this case a belt conveyor) is fitted with an electronic belt scale, used to measure the weight of asphalt being conveyed. The on-board computer is programmed to supply the correct amount of asphalt to form a windrow by monitoring the individual speed of the auger. Gradually, as the pug mill""s discharge rate increases (greater volume of asphalt being processed), the on-board computer proportionally reduces the flow of new asphalt by monitoring the individual auger""s speed, measuring the volume of material exiting the pug mill""s variable ski (asphalt volume measurement and the amount of weight on the conveyor belt""s scale).
Once the windrow has been established by monitoring the flow of asphalt through the pug mill, the on-board computer automatically switches to its Remix program. The surge bin/vertical elevator is used to scalp off a percentage of 100%, recycled asphalt in the windrow. An adjustable (proportional) electronic sensor is used to set and control the scalping depth of the vertical elevator, allowing the elevator to follow the varying windrow""s height. The belt conveyor and the front hopper""s drag chain start supplying new asphalt to the hopper/diverter valve, allowing the two asphalt flows to blend together in the vertical elevator""s slats. The central belt conveyor is fitted with an electronic belt scale, used to measure the weight of asphalt being conveyed. The on-board computer is programmed to calculate and control the correct amount of new asphalt being blended into the 100% recycled asphalt (10% to 15%). This is accomplished by measuring the volume of material exiting the pug mill""s variable ski (material volume measurement and the amount of weight on the conveyor""s belt scale. The variable speed, drag chain in the front hopper and the variable speed central, belt conveyor supplies the correct amount of new asphalt. The belt conveyor is designed to operate at a higher speed than the hopper drag chain, preventing spillage at the drag chain""s discharge point on to the belt conveyor. The two conveyors are fitted with optical encoders to monitor the speed of both units, allowing the on-board computer to monitor and control the speed ratio between the two conveyors. As the amount of new asphalt increases or decreases, based upon the volume of asphalt being recycled the vertical elevators speed is proportional changed to pick up more or less recycled asphalt. This is possible as the inlet to the vertical elevator is always flooded (built up) with asphalt. The blend of recycled and new asphalt is delivered to the heated and insulated surge bin. The on-board computer, monitoring the weight of the bin will always try and maintain the bin at 50% of its capacity. This is achieved by automatically controlling the discharge flow from the surge bin""s two, rotary valves, by monitoring the individual screed auger""s speed (auger/divider/strike off blade assembly). The auger with the highest speed will receive proportional, more asphalt. By blending the new asphalt with a proportion of the 100% recycled asphalt (picked up from the windrow) in the surge bin/vertical elevator provides a little more mixing than would otherwise be possible if the hopper/diverter valve dumped asphalt directly on to the windrow. If the extra blending (mixing) is found not to be required then the asphalt can be diverted and dropped on to the 100% recycled asphalt""s windrow. It should be noted that the augers do mix the asphalt as it is moved across the front face of the screed assembly. One might ask why not introduce the new asphalt onto the mills or the pug mill. Pre-engineering, using core samples, taken at regular intervals, determine how much rejuvenator fluid and/or polymer liquid must be added by the Recycling Machine and how much washed aggregate the final Preheater must add. Adding new asphalt would complicate the testing procedure.
5. Inability to process asphalt around utility structures and obstructions.
Utility structures and other obstructions have until now presented one of the greatest challenges to the HIR of asphalt, especially in city work. An example would be a utility structure located in the center of the lane being processed. To prevent damage to the Recycling Machine""s carbide milling teeth (main and extension mills) and to the iron utility structure(s) located in the asphalt""s surface, the mill(s) are lifted, leaving an unprocessed section of asphalt across the width of the lane. When dealing with utility structures and obstructions the following methods are typically used:
a. Ignore the problem. Raise the scarification and/or mill systems and let the screed assembly place recycled asphalt on top of the old asphalt. The result is a width of asphalt up to 1 m (3 ft.) or more in length (in the direction of travel) that has not been recycled (rejuvenated) to pre-engineered specifications. The section will not be compacted to the same degree as the recycled asphalt by the rolling equipment, thus leaving a bump in the mat (asphalt surface) of old asphalt
b. Raise the scarification and/or mill systems and use hand tools (rakes and shovels) to loosen the old asphalt. This is almost impossible without stopping the recycling machine and is dangerous to workers, as they must reach into the processing area of the machine. Recycling machines that have scarification systems that float over and around obstructions have been somewhat successful as the asphalt is loose enough to hand move (where possible) without stopping the Recycling Machine. The asphalt remaining on the heated surface mixes with the recycled asphalt, collected and stored in front of the screed assembly. The asphalt picked up by hand shovel is generally, thrown back into the mills for processing.
c. Before 100% HIR of the asphalt surface the area around the obstruction(s) is cold milled with a small milling machine. The milled asphalt is collected and removed and the surface is swept if processing is to be conducted at a later date. This works well, except that a reduction in the volume of material available for recycling occurs, resulting in new asphalt having to be added or a change in profile/grade at the time of recycling. Filling the cold milled sections with new virgin asphalt and compacting before recycling works well, but presents compaction problems (bump in surface) and in some cases, changes to the finished mat""s surface texture. The major objection to this approach is the added cost, traffic delays and possible driving hazard due to the open, milled sections, if not paved immediately.
d. Recycling machines that produce a windrow of asphalt (screed assembly removed) for pickup by a windrow conveyor, attached to a standard paving machine have a greater opportunity to work around utility structures and obstructions. To date hand-tools, powered machines and even a hydraulic arm fitted with a blade, mounted to the windrow conveyor, scrape and collect the unprocessed asphalt. The hydraulic arm requires the windrow conveyor/paving machine to stop, marking the finished mat (the screed sinks into the asphalt surface due to it""s own weight, vibration from the windrow conveyor and the operation of the hydraulic arm). Other problems exist when using a separate windrow conveyor and paving machine, i.e. increased costs, reduced asphalt temperature, increased segregation, increased pollution and increased equipment train length. In addition, the proper mixing of the old asphalt (asphalt scraped from the heated surface) does not take place as the old asphalt is generally placed on to the open windrow, throwing off the quality of the recycled asphalt contained within the windrow. Safety is another issue when processing with an open windrow. It is quit common for automobiles to try and cross the heated windrow only to become stuck in 250 to 300+ Deg F. asphalt. Animals have seriously burnt their feet, as have humans with open footwear! Recycling machines with an attached screed do not suffer from the above problems, as there is no open windrow.
The present invention scarifies and cleans around utility structures and obstructions without stopping the HIR Recycling Machine, allowing the scarified asphalt to be collected and properly mixed with additives:
The rake scarification/blade collection system fitted to the final Preheater (Preheater ahead of the Recycling Machine) and the Recycling Machine are identical. The blades are attached to the four, main rake, pivoting bodies, located behind the spring loaded, carbide cutters attached to the same bodies. When approaching a utility structure or obstruction (Preheater followed by the Recycling Machine) the Preheater""s operator tilts the required, individual rake bodies, leaving the carbide cutters in the heated asphalt while at the same time lowering the trailing blades. Hydraulic force pushes the blades into the scarified surface 50 mm (2xe2x80x3) or more, scraping and collecting the heated asphalt. Once past the utility structure/obstruction, the blades are raised at a controlled rate (rate is adjustable and once set is automatic), releasing the collected asphalt in a 50 to 75 mm (2 to 3xe2x80x3) layer. Raising the blades does not effect the operation of the carbide cutters. Hand tools or a small two-wheel drive machine with adjustable blade, similar to a walk behind rotovator (without the rotor) are used (if required) for the final cleanup with the asphalt being spread on to the heated, scarified surface ahead or behind the area being scraped and cleaned. Plenty of space and time exists for this process as the Recycling Machine is generally trailing the Preheater by up to 9 to 12 m (30 to 40 ft.). The Recycling Machine""s rake blades are available if further cleaning is required when approaching the same utility structure/obstruction using the same procedure as used by the Preheater. Raising the main mill on the Recycling Machine for utility structures/obstructions will automatically stop the flow of rejuvenator fluid to the main mill and the pug mill, preventing the fluid from reaching the milled, base surface, thereby eliminating eventual bleeding of the finished, compacted surface. When the main mill is manually raised for utility structures/obstructions, the on-board computer calculates and stores in it""s memory the amount of rejuvenator fluid that would have been sprayed into the asphalt being recycled, if the main mill had not been raised. When the main mill is lowered (taken off manual control) into the heated surface (controlled again by the automatic grade/slope controls) it collects and feeds the asphalt into the pug mill for final mixing. Lowering of the main mill allows the rejuvenator fluid flow to commence. The stored (memory) amount of rejuvenator fluid, together with the required processing amount of fluid (determined by the pug mill) results in increased fluid flow required for the increased volume of asphalt at that particular section (rake scarified asphalt covered with a layer of asphalt collected by the rake blades). The ratio of rejuvenator fluid to asphalt being recycled remains consistent.
Blades are not required on the extension rakes as the extension mills are fully adjustable (raise/lower, in/out and tilt up/down) and can be used to cut and clean around most utility structures/obstructions in their path. The extension mills are fitted with a cutter blade at each outer end, providing cleaning to the edge of utility structures/obstructions and curbs and gutters. Final cleaning on each side of the Recycling Machine is easily accomplished with hand tools, even while moving.
The above, innovations allows any processing work required around utility structures and obstructions to be accomplished before the Recycling Machine recycles the old asphalt, rather than after recycling and result in the following advantages:
The old asphalt that has been moved from around utility structures, obstructions and sections across the asphalt""s surface (where the mills can not be used) remains on the surface for 100% processing by the Recycling Machine.
The complete width of the asphalt can be checked and worked upon. This is not the case after the Recycling Machine has processed the asphalt as the wide (approximately 36xe2x80x3) windrow covers the center section of the width.
6. Inaccurate and inconsistent application of liquid additives.
While other 100% HIR equipment have systems designed to monitor and control the application of rejuvenator fluid into the reworked (recycled) asphalt, none appears to have the ability to monitor and control the application of liquid polymers together with rejuvenating fluid. Generally, recycling machines control the rejuvenator""s application rate by monitoring the machines processing speed (distance traveled). Distance traveled, by itself, produces inaccurate and inconsistent results as the volume of asphalt being processed changes constantly as density, depth of cut, pavement profile and width of cut (machines with variable width heating, scarification and milling systems) all vary.
The problem is solved by a liquid distribution system using two or more positive displacement, diaphragm pumps. The pumps accurately meter light (unheated) and heavy (heated) rejuvenator fluids and liquid polymers. Ground speed sensing (distance traveled) and application rate (manually input into the on-board computer using pre-engineered data) together with asphalt volume sensing and temperature correction factors, provide accurate and consistent results, which are verifiable through laboratory testing.
7. Inaccurate and inconsistent application of the aggregate.
The present invention and methods often uses a plurality of Preheaters. Often three or more Preheaters are used, operating ahead of the AR Recycling Machine to soften the asphalt surface to a depth of 50 mm (2xe2x80x3) or more. The final Preheater is fitted with a rake/blade scarification/collection system and aggregate distribution system.
In prior processes, the machine""s processing speed (distance traveled) is generally used to control the aggregate""s distribution rate. Distance traveled, by itself, provides inaccurate and inconsistent application rates as the volume of aggregate being spread must be constantly changed as the volume of asphalt pavement being recycled constantly changes due to variations in processing depth (profile) and width.
The problem is solved by the present invention through the spreading washed aggregate (sand, small stone, steel mill slag etc.) directly on to the heated asphalt surface by an aggregate distribution bin (controlled and monitored by the onboard computer) attached to the final Preheater. Ground speed sensing and application rate (manual input into the on-board computer using pre-engineered data), together with proprietary width measurement (width of asphalt being processed) and asphalt surface profile sensing, provide accurate and consistent results, which are verifiable, through laboratory testing.
8. Improper mixing of rejuvenator fluid, washed aggregate and reworked (recycled) asphalt:
The amount of time available for mixing has until now, been inadequate to produce a homogeneous mix. To date the mixing of rejuvenator fluid and aggregates into the reworked asphalt is generally accomplished by one of the following methods:
a. The heated, milled asphalt is removed from the surface and conveyed to a pug mill on-board the recycling machine where mixing (rejuvenator fluid and aggregate) takes place as a continuous or batch process. The pug mill discharges the asphalt into the front hopper of a standard paving machine (attached to the recycling machine) or in front of the recycling machine""s screed assembly for final placement and compaction. Aggregate segregation, loss of heat and emissions are all increased.
b. The recycling machine mills and collects the heated asphalt and aggregate (if added) while leaving it on the heated surface. The collected, milled asphalt/aggregate passes into an in-line pug mill or mixing auger. The pug mill or mixing auger discharge is generally unrestricted, resulting in reduced retention (less mixing) of the recycled asphalt and additives and increased segregation caused by the larger aggregate (stone) rolling down the windrow""s sides.
c. Scarification systems (no mills, pug mill or other mixing devices) use cutters to penetrate into the heated asphalt""s surface while aggregate and rejuvenator fluids are spread directly on to the heated asphalt. The only mixing that takes place is by the action of the cutters and to some degree, the action of the screed""s distribution auger. Limited and inconsistent mixing result, as the scarified asphalt and additives are not collected and mixing by any mechanical apparatus.
The crown and curb (left and right) side, recycled asphalt, are not completely mixed together to form a homogeneous mix (only applies to processes where the asphalt is not removed from the surface). Dirty, curbside recycled asphalt will show up in the finished mat (asphalt behind the screed assembly) on the curbside section as discolored asphalt (dull, as the dirt/dust absorbs more of the asphalt""s liquid). Sweeping the asphalt surface reduces the buildup of dirt and dust, but cannot remove it completely from the cracked or porous asphalt.
The fine aggregates contained in and added to the recycled asphalt remain behind the mill(s), mixing auger or pug mill (if fitted) as a fine layer on the milled surface. To obtain a homogenous mix, all of the reworked asphalt and additives require collection for mechanical mixing.
The following innovations found in the present invention increase the mixing and/or mixing time in the HIR Recycling Machine:
a. Three or more Preheaters, operating ahead of the HIR Recycling Machine softening the asphalt surface to a depth of 50 mm (2xe2x80x3) or more. The final Preheater is fitted with a rake/blade scarification/collection system and aggregate distribution system. The rake/blade system is the first of the processing equipment to break the heated asphalt""s surface, releasing moisture (steam) and loosening the heated asphalt. The rake""s carbide cutters form grooves 50 to 75 mm (2-3xe2x80x3) or more into which the washed aggregate (sand, small stone, steel mill slag etc.) falls. Spreading the damp aggregate on to a heated surface in a thin, ribbed layer not only allows any moisture to evaporate quickly, it also promotes greater mixing by the Recycling Machine""s rakes, mills and pug mill. The deposited aggregate starts to absorb liquid asphalt from the heated asphalt (asphalt to be recycled) before being processed by the heating, milling and mixing stages.
b. The Recycling Machine""s heating system (heater box) features flexible, stainless steel mesh skirts around the parameter of the heater box to retain heat. The skirts are also designed to touch (drag) the heated asphalt""s surface. The front skirt spreads the aggregate (applied by the final Preheater) into a thin layer. The Recycling Machine""s heater box gently applies additional heat to the spread aggregate and asphalt surface, thereby removing any remaining, trapped moisture. Excess moisture in any part of the mixing process will prevent the proper coating and adhesion of existing asphalt binders, additional rejuvenator fluid and polymer liquid to the aggregates contained in or mixed into the recycled asphalt. The rake/blade system attached to the Recycling Machine further mixes the added aggregate and heated asphalt before the milling/mixing stages.
c. The Recycling Machine""s extension mill and main mill rotors (rotating carbide cutters) all feature shallow fighting designed to reduce the rotors material conveying efficiency. Attached to backside of the lighting are replaceable carbide cutting teeth and holders. The shallow lighting, together with the carbide cutters (rotating in a down-cut direction), causes the heated/milled asphalt to build up in front of the rotors rather than immediately being conveyed away. Rejuvenator fluid added at the main mill""s rotor and aggregates distributed on to the heated asphalt surface, ahead of the 100% HIR Recycling Machine (by final Preheater) are continuously mixed by the main mill""s carbide teeth. The main mill""s material discharge is offset to one end of the rotor. The rotor provides premixing of the old (recycled) asphalt, rejuvenating fluid and aggregate before discharging into the offset front rotor of the pug mill.
d. The offset front rotor of the pug mill (receives material from the main mill""s offset discharge) is equipped with carbide-faced paddles (two per arm) arranged in a spaced, spiral pattern. The spaced, spiral pattern reduces material conveying efficiency, increases dwell time and the mixing action of the recycled asphalt and additives. The spiral section of the pug mill""s offset front rotor feeds the recycled asphalt and additives into the pug mill""s mixing chamber. The offset front rotor is also equipped with carbide faced, paddles (two and four per arm), arranged in an alternating left and right hand pattern (located in the mixing chamber). The spiral section and the alternating paddle section of the offset front rotor receive rejuvenator fluid and if required, polymer additive. The recycling Machine""s onboard computer automatically controls (stages) the application of rejuvenator fluid and liquid polymer. The main mill is the first to receive rejuvenator fluid followed by the pug mill""s front rotor (spiral section) and finally the alternating paddle section of the pug mill""s front rotor. Liquid polymer is only sprayed into the pug mill when rejuvenator fluid flow is established in the main mill and/or the pug mill. Staging the rejuvenator fluid""s application to the processed asphalt""s flow through the mills and pug mill provides increased mixing time, greater coverage and less chance of the fluid additives coming into contact with the milled, base surface. The pug mill""s offset front rotor completely mixes the left and right (crown and curb) side asphalt while the pug mill""s rear rotor completes the final mixing and discharge of the asphalt into a formed windrow. The pug mill""s rear rotor (discharge rotor) diameter is greater than the front rotor and is equipped with carbide-faced paddles (two and four per arm) arranged in an alternating left/right hand pattern. The front and rear rotors do not intermesh, allowing the rotor speeds to be set individually for varying, asphalt specifications. Both design features increase the throughput of recycled asphalt and promote increased mixing/tumbling and moisture (steam) release.
e. An adjustable trip blade is located between the pug mill""s front and rear rotor assemblies. The trip blade is the full width of the mixing chamber. The trip blade scrapes the milled, base surface, lifting any asphalt and additives missed by the front rotor assemblies paddles (the rotor paddles do not make contact with the milled base). As paddle tip wear increases the amount of asphalt missed would increase, reducing the mixing efficiency of the pug mill. Rejuvenator fluid (polymer additives were not tried) could not be sprayed into the prototype pug mill as the fluid would come into direct contact with the milled base surface in the mixing chamber and would not be collected and mixed by the rotor assemblies paddles. Bleeding of the finished mat (the width of the pug mill mixing chamber) resulted when using rejuvenator fluid. The trip blade improves mixing and allows rejuvenator fluid and polymer liquid to be sprayed directly into the pug mill""s front rotor assembly. Competitive recycling machines fitted with a mixing auger or standard pug mill do not scrape the base surface in the mixing chamber or in the case of a mixing auger, the discharge section. The result is incomplete mixing, especially as rotating components wear. An external, single screw adjuster sets the trip blade""s height. A hydraulic cylinder connects the trip blade to the screw adjuster. The hydraulic cylinder allows the trip blade to rotate if contact with a utility structure occurs, preventing damage to the trip blade and utility structure. The trip blade resets automatically.
f. The asphalt being discharged out of the pug mill is restricted through a variable (mechanical) opening (parallelogram ski) located behind the pug mill""s rear rotor assembly. The ski is hydraulically adjustable for pre-load (vertical pressure exerted on to the asphalt windrow) and provides light compaction to the windrow and resistance to asphalt flow through the pug mill. The ski also measures the volume of asphalt exiting the pug mill and generates a proportional electronic signal used in calculating the required amount of rejuvenator fluid and polymer liquid to be added to the reworked (recycled) asphalt. Other recycling machines do not restrict the asphalt""s flow to improve mixing or compact the windrow to reduce segregation.
g. Discharge from the pug mill""s rear rotor is to the centerline of the Recycling Machine. Testing has shown that central discharging mills (not offset), even when used with an efficient in line pug mill or mixing auger (mixing on the milled surface) will not achieve complete crown and curbside mixing of the asphalt/additives into a homogeneous mix. The offset main mill""s rotor assembly together with the pug mill""s offset front rotor and rear rotor assemblies, completely mix the crown and curbside asphalt into a homogeneous mix.
h. Spring loaded (floating) blades located behind the extension mills, main mill and pug mill collect the fine aggregates and fluid additives by scraping the milled surface. The blades (replaceable) are adjustable in height to compensate for blade wear and carbide rotor teeth (replaceable) wear. The springs keep the blades forced down on to the milled surface and also provide protection against damage to iron utility structures by allowing the blades to ride up and over the utility structure. Scraping the milled, asphalt surface collects the finer aggregates and liquid additives, thereby producing a consistent and homogeneous asphalt mix. Other recycling machines generally use fixed blades or no blades, resulting in a remaining layer of fine aggregates and liquid additives on the milled surface. Liquid additives remaining in direct contact with the milled surface produce bleeding of the finished mat (streaks).
9. Inability to remove moisture from reworked asphalt
Moisture removal in prior systems is limited due to inadequate heat penetration, insufficient mechanical mixing and the lack of moisture extraction systems. The positive removal of moisture (steam) at the mills and pug mill or mixing auger is generally, not used.
Moisture removal in the present invention may be done in four stages:
a. Three or more Preheaters, operating ahead of the Recycling Machine softening the asphalt surface to a depth of 50 mm (2xe2x80x3) or more. The final Preheater is fitted with a rake/blade scarification/collection system. The rake/blade system is the first of the processing equipment to break the heated, asphalt surface, releasing moisture (steam) and loosening the asphalt without damaging the asphalt""s larger aggregate. The rake""s carbide cutters are hydraulically adjustable for down force (pressure compensated), are spring-loaded and mounted on pivoting frames, allowing the cutters to follow varying pavement profiles and scarify around iron utility structures. Penetration into the heated asphalt is generally deeper than the Recycling Machine""s main and extension mill profiling depth. The Preheater""s rake/blade carbide cutters loosen the asphalt, allowing the trapped moisture (steam) to release before further scarification, milling and mixing by the Recycling Machine""s rakes, mills and pug mill.
b. The Recycling Machine""s electronically controlled and monitored heating system produces convection and infrared heating and is used to drive off any remaining moisture in the added aggregate (damp, washed sand, deposited on to the heated asphalt by the final Preheater""s aggregate distribution system). The Recycling Machine""s rakes/blades are identical in design and operation to the Preheater""s rakes/blades and produce further mixing of the aggregate into the heated asphalt. The rakes also cut deeper into the loosened asphalt, releasing more moisture in the form of steam.
c. Automatic grade/slope sensors control the depth of cut of the extension and the main mills. The mills mill and tumble the loosened, heated asphalt, mixing additives and releasing steam. A venturi (using the heater box blower air supply to create a negative air pressure) draws steam through the main mill""s enclosed support frame, venting it to the top of the Recycling Machine.
d. The offset pug mill is fitted with a moisture extraction system. A venturi (as above) creates a negative air pressure in the pug mill""s mixing chamber. The pug mill""s front and rear rotors tumble and mix the restricted asphalt enclosed in the mixing chamber. The air extraction system reduces the moisture level in the reworked (recycled) asphalt by drawing off and venting the released steam to the top of the Recycling Machine.
10. Inconsistent depth differential between the 100% recycled asphalt and the new asphalt when using the integral overlay method.
Integral Overlay recycling machines have been around for many years. They are popular with contractors as the new asphalt can be used to hide the poorly recycled asphalt below and still produce a very good looking, new surface that generally stands up well over time. It is possible to hide all sorts of imperfections, as it is difficult to sometimes see the recycled surface as the secondary screed assembly is laying new material directly on to it. However, in prior systems and processes, three major problems are generally encountered:
a. The quality of heat produced by the preheaters and the recycling machine are incapable of producing a deep penetrating heat, without setting the asphalt""s surface on fire.
b. The recycled asphalt could not be processed using pre-engineering specifications as the machine was manually operated with no on-board computers to monitor and control the recycling process.
c. The depth differential between the recycled asphalt and the new asphalt was inconsistent.
The following innovations of the present invention allow the Recycling Machine with Integral Overlay to 100% recycle existing asphalt while laying a high quality, new asphalt surface to grade, while meeting the smoothness tests.
The Recycling machine is equipped with the same, two grade control systems, as described earlier on.
The front asphalt hopper and central belt conveyor are the same as for 100% HIR method, except that a short, shuttle conveyor is used to supply new asphalt to the rear, secondary auger and screed assemblies. The level of asphalt in the secondary auger and screed assembly controls the asphalt""s flow from the front hopper and central belt conveyor assemblies. A proportional, electronic sensor (located in the feed chute used to supply asphalt to the secondary auger) signals the on-board computer to speed up the front asphalt hopper""s and central belt conveyor""s discharge rate. The position of the shuttle conveyor can be manually, or, automatically controlled by the on-board computer allowing new asphalt (delivered by the central conveyor) to spill into the primary auger/divider/strike off blade assembly when insufficient recycled asphalt is available to maintain the correct head of asphalt in front of the primary screed assembly. The design of the shuttle conveyor allows new asphalt to be delivered to both the primary and secondary auger and screed assemblies at the same time.
The primary auger/divider/strike off blade is identical in operation and control, as described earlier on.
The primary and secondary screeds are attached to the Recycling Machine""s mainframe by screed arms attached to a left and right side adjustable tow points in the same manner as described earlier. The only difference being the length of the screed arms used on the primary and secondary screeds.
The major difference is in the control of the primary and secondary screed""s grade and slope control system. Both the primary and secondary screed arms are attached to the same tow point (one on either side of the machine,) which can either be pinned into position, or controlled by the automatic grade control system, as described earlier. Topcon""s Smoothtrack(copyright) 4 Sonic Tracker II(trademark) averaging beams and electronic slope sensor are again used, as described earlier, however the averaging beams and electronic slope control are only attached to the secondary screed""s (rear screed) screed arms. The secondary screed assembly is allowed to float and features the same weight transfer system, as described earlier. The primary screed assembly requires no grade, or slope controls and is also allowed to float, but not to the same degree as the secondary screed assembly. The primary screed assembly senses the position of the secondary screed assembly through two, proportional, electronic or hydraulic sensors. The sensors are attached to the left and right side of the secondary screeds tow arms and sense the position of the left and right side of the primary screed""s tow arms. The height of the sensor plates can be adjusted to set the height differential between the primary and the secondary screed assemblies, which is generally xc2xdxe2x80x3 to 1xc2xdxe2x80x3. The two screed sensors send information to the on-board computer, which in turn, operates two hydraulic, 4 way proportional, directional control valves. The secondary screed assembly is the master while the primary is the slave and tries to match every move made by the secondary screed assembly (master). To accomplish this the primary screed assembly is attached to the Recycling Machine""s mainframe by two identical, hydraulic cylinders, used to attach the secondary screed to the mainframe. The four hydraulic cylinder""s prime function is to raise and lower both screed assemblies. The secondary screed assembly cylinders are allowed to float (move up and down freely) as all of the cylinder""s hydraulic ports are connected to tank (return) when laying asphalt. The primary screed assembly cylinders are also allowed to float; however the hydraulic cylinder""s ports are connected to tank through flow control valves. The system works in the following manner: At the start of the recycling operation the Recycling Machine is backed up to the previously finished joint that has been preheated. The secondary screed assembly is lowered on to starting blocks and the screed cranks are nulled out (neutralized) and set. The primary screed assembly is lowered on to the asphalt""s surface and the screed cranks are nulled out and then given one turn up, to slightly raise the front of the screed""s plates. This setting will allow the screed assembly to automatically rise when asphalt builds up in front of the screed. The machine operator places the Recycling Machine into automatic mode, allowing the on-board computer to monitor and control all of the automatically programmed operations. Asphalt is delivered from the front asphalt hopper, by the central conveyor to the shuttle conveyor. The shuttle conveyor supplies asphalt to the secondary screed augers. The augers feed the asphalt out to the ends of the secondary screed""s extensions until the electronic asphalt sensors, attached to the screed extension""s end plates stop the augers (the asphalt is at the correct level). Once the secondary auger and screed assemblies have been fully supplied with new asphalt the on-board computer moves the shuttle conveyor allowing new asphalt to spill into the primary auger/divider/strike off blade assembly. New asphalt will be delivered until the electronic asphalt sensors, attached to the primary screed extension""s end plates stop the augers (the asphalt is at the correct level). At this position the secondary screed assembly is at a higher position than the primary screed assembly. The secondary screed""s tow arm sensors are signaling the on-board computer to power the two proportional, directional control valves that send hydraulic oil to the primary screed""s two hydraulic cylinders. The primary screed assembly is trying to be raised by hydraulic pressure, however this is not possible, as the hydraulic pressure is set at a low pressure, preventing the screed assembly from being raised. The operator then puts the processing equipment (scarification rakes, mills, pug mill, rejuvenator and heating system) into operation and moves the Recycling Machine briskly away, preventing the secondary screed from settling into the new asphalt while the primary screed assembly rises due to the asphalt in front of the screed assembly and also the limited hydraulic pressure trying to lift the screed. The front asphalt hopper will automatically provide new asphalt, on demand, to the primary and secondary screed assemblies. As the Recycling Machine starts to 100% recycle and rejuvenate the heated asphalt, as discussed previously, the primary auger/divider/strike-off plate begins to split and convey the windrow of 100% recycled asphalt, out to the primary screed""s extensions. As the primary screed was rising, hydraulic oil was being forced out of the partially restricted cylinders through the cylinder""s head end ports and flow control valves. The oil being supplied from the proportional valves (variable flow controlled by the sensor""s outputs) to the rod end of the cylinders is also flowing through the rod end, flow control valves. The greater the flow of hydraulic oil from the proportional valves, the greater the differential in pressure across the flow control, valves. The screed sensors will eventually turn off the proportional valves when the primary screed assembly reaches the set point (differential height). The control of the system is to slowly change the forces working on the primary screed assembly, keeping it at the set, height differential. The sensors only respond when the primary screed tries to move away from the set differential. An example would be when the head of asphalt in front of the primary screed increases as the Recycling Machine mills through a high section. The primary auger/divider/strike off blade would hold back and control most of the mass, however there will be more asphalt reaching the screed (due to the pressure of the buildup), which will causes the screed to rise. When the reverse happens (lack of material), the screed will sink. As noted before the hydraulic pressure is too low to keep the screed raised and at the correct level. This is not a problem, as the secondary screed will continue to set the correct grade by laying a greater amount of new asphalt. This condition will rarely occur as the on-board computer monitors the primary auger/divider/strike off blade""s individual auger""s speeds and allows the shuttle conveyor to spill extra, new asphalt into the augers, maintaining the head of asphalt in front of the primary screed assembly. When using the Integral Overlay process, the primary screed assembly should be prevented from exceeding the height of the secondary screed. If this were allowed to happen, the 100% recycled asphalt would replace the new asphalt. To prevent the primary screed assembly from getting into this position the hydraulic pressure used for down force on the primary screed""s hydraulic cylinders is set to a higher pressure than the pressure used to raise the screed assembly. This is possible as the Recycling Machine is heavy and will not by lifted by the pressure in the primary screed""s hydraulic cylinders.